Ha, you tricked me.. I was looking at the println and thinking.. you don’t really want those there.. do you???? But I assumed you had that covered… so.. stupid makes two…. ;-)
— Kirk > On Dec 27, 2017, at 11:23 AM, Peter Veentjer <[email protected]> wrote: > > Hi Kirk, > > thanks for your reply. > > Unfortunately I'm made a very shameful mistake. The println at the end of the > loop always gets called; even if nothing is found. And I made the content so > that the query would not find anything since I'm currently not yet able to > return a result. So the initial loop never has a println and the second loop > always has a println. > > After I added a guard to the println in the second loop, the performance of > both loops is exactly the same. So it wasn't a JIT issue after all, but just > plain stupidity. > > On Wednesday, December 27, 2017 at 11:21:05 AM UTC+2, Kirk Pepperdine wrote: > Hi, > > > Can you make count a field and rerun? Not sure the for loop is being unrolled > in either case as the index is a long. I’ve not checked unrolling but using a > long can cause the JIT to miss optimizations that it would normally apply if > an int was used instead. You might want to see what JITWatch can tell you. > > — Kirk > >> On Dec 27, 2017, at 10:09 AM, Peter Veentjer <[email protected] >> <javascript:>> wrote: >> >> As part of an experiment, I'm working on querying large volumes of data >> which is stored offheap. >> >> The content of each record is stored in a chunk of offheap memory. So >> instead of having an array of object references, it is an array of records >> (no pointer chasing). >> >> My confusion is about some code I'm generating based on the query content. >> There are 2 flavors; one flavor where I'm printing if I found something and >> the other flavor increments a local long variable and print this at the end >> of the loop. >> >> The strange thing is that the first one (printing when the correct entry is >> found), is 15x faster than the one where I'm increasing the local counter. >> >> So this is the first: >> >> import java.util.*; >> public class FullTableScan_e872b2bd8f274cc18b37ac2a0e3df2ed extends >> com.hazelcast.simplemap.impl.FullTableScan{ >> public void run(){ >> long offset=slabPointer; >> for(long l=0;l<recordIndex;l++){ >> if((unsafe.getInt(offset+12)==10000) && >> (unsafe.getBoolean(null,offset+16)==true)){ >> System.out.println("found"); >> } >> offset+=recordDataSize; >> } >> >> } >> public void init(Map<String, Object> binding){ >> } >> } >> >> >> And this is the second: >> import java.util.*; >> public class FullTableScan_e872b2bd8f274cc18b37ac2a0e3df2ed extends >> com.hazelcast.simplemap.impl.FullTableScan{ >> public void run(){ >> long offset=slabPointer; >> long count = 0; >> for(long l=0;l<recordIndex;l++){ >> if((unsafe.getInt(offset+12)==10000) && >> (unsafe.getBoolean(null,offset+16)==true)){ >> count++; >> } >> offset+=recordDataSize; >> } >> System.out.println("count:"+count); >> } >> public void init(Map<String, Object> binding){ >> } >> } >> >> What could be the reason of this huge performance difference? It isn't a >> warmup problem since it was running for 5 minutes. Could there be some data >> dependency with the second loop that prevents the loop to be unrolled? I >> should analyze the assembler; perhaps this will shed some light on the >> situation. >> >> -- >> You received this message because you are subscribed to the Google Groups >> "mechanical-sympathy" group. >> To unsubscribe from this group and stop receiving emails from it, send an >> email to [email protected] <javascript:>. >> For more options, visit https://groups.google.com/d/optout >> <https://groups.google.com/d/optout>. > > > -- > You received this message because you are subscribed to the Google Groups > "mechanical-sympathy" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected] > <mailto:[email protected]>. > For more options, visit https://groups.google.com/d/optout > <https://groups.google.com/d/optout>. -- You received this message because you are subscribed to the Google Groups "mechanical-sympathy" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. For more options, visit https://groups.google.com/d/optout.
